Entangling one polariton with a photon: effect of interactions on a single-polariton quantum state

TL;DR

This paper reports the first experimental demonstration of a genuinely quantum behavior of single microcavity polaritons, showing how interactions influence their quantum state, with implications for quantum information processing.

Contribution

It introduces the first experimental swap of a photon with a polariton in an entangled state, revealing quantum effects at the single-polariton level influenced by interactions.

Findings

Successful swapping of a photon for a polariton in an entangled state

Observation of interaction effects on single polariton quantum states

Demonstration of polaritons' potential for quantum information applications

Abstract

Polaritons are quasi-particles originating from the coupling of light with matter that demonstrated quantum phenomena at the many-particle mesoscopic level, such as BEC and superfluidity. A highly sought and long-time missing feature of polaritons is a genuine quantum manifestation of their dynamics at the single-particle level. Although they are conceptually perceived as entangled states and theoretical proposals abound for an explicit manifestation of their single-particle properties, so far their behaviour has remained fully accountable for by classical and mean-field theories. In this Article, we report the first experimental demonstration of a genuinely-quantum manifestation of microcavity polaritons, by swapping, in a two-photon entangled state generated by parametric down-conversion, a photon for a polariton. Furthermore, we show how single polaritons are affected by polariton-polariton interactions in a propaedeutic demonstration of their qualities for quantum information applications.